The present invention relates to an improved method and apparatus for placing retrofit dowels between adjacent concrete structures, such as pavement slabs. In its more specific aspects, the invention is concerned with an improved combined end cap and chair for supporting a dowel within a groove formed between the structures, which end cap and chair functions both to support the ends of the dowel and to provide a space into which the dowel may expand.
When a Department of Transportation, such as Caltrans of California, wants to add additional concrete paving, or to repair damaged concrete pavement, it uses retrofit dowels in the existing pavement. Such dowels are installed by sawing grooves in the pavement and then dropping the dowels into the grooves. The grooves are generally about 24 inches long, 2xc2xd inches wide, 8 inches deep and 12 inches on center. The grooves are cut across adjacent sections of the pavement and ultimately, with the dowels received therein, serve to hold the sections in alignment. The dowels must be positioned parallel to each other and parallel to the top surface of the pavement. They must also be held off the bottom of the groove so that grout can surround them. In addition, they must have a space at each end of the dowel to allow for expansion or contraction.
FIG. 1 shows a typical prior art arrangement where a groove has been sawed between adjacent sections of concrete pavement and a dowel has been placed in the groove. In this arrangement, the dowel is spaced off the bottom of the groove with a rebar chair adjacent each end of the dowel. Plastic caps are provided on the ends of the dowel to create void to either end of dowel. The assembly of the dowel, caps and chairs is manually centered in the groove. Grouting is then filled into the groove and consolidated. If the ends of the dowel are pushed down, while placing the grout or the vibrator used to consolidate the grout, the dowel will fulcrum around one of the chairs and not remain parallel to the top of the pavement.
The prior art also teaches concrete slab dowel systems which are cast in place and employ sleeves received around the dowels which include collapsible spacers at the ends of the dowels to accommodate for relative expansion and contraction of the dowels and concrete. Such an arrangement may be seen, for example, in U.S. Pat. No. 5,797,231.
The apparatus of the present invention is concerned with a cap for engagement over the end of a dowel to be placed within a retrofit groove formed in and extending across adjacent sections of a concrete structure. The cap has an interior chamber with one end thereof open for receipt of an end portion of the dowel and the opposite end thereof closed. Retaining means is provided to secure the cap against inadvertent displacement from the dowel and positioning means on the interior of the cap establishes spaced relationship between the end of the dowel and the closed end of the cap to provide a space into which the dowel may expand. The positioning means is displaceable to enable the spaced relationship to be reduced in response to excessive relative forces being applied to the cap and the dowel. A foot is provided on the cap to support a dowel received within the cap in spaced relationship to the bottom of the groove.
The invention is also concerned with an assembly comprising a dowel having such end caps engaged over its ends to provide for support of the dowel at its end portions in a condition generally parallel to the bottom of a groove within which the dowel is received. The method of the invention includes the steps of forming the groove across the sections of the concrete structure to be doweled together and positioning the dowel and end cap combination within the groove so that it is supported in spaced relationship to the bottom of the groove by the feet on the end caps. After placement of the dowel, the groove is filled with grout and the grout is compacted.
The invention is also concerned with the provision of wings on the end cap positioned to engage the sides of a groove within which the cap is received to maintain the cap in secure centered relationship relative to the groove. Ideally, the cap is constructed so as to enable the position of the end of a dowel received therein to be visually observed. This may be provided, for example, by fabricating the cap of a translucent material.
A principal object of the invention is to provide for the support of a dowel in a groove extending between adjacent concrete structures in a manner which prevents the dowel from lifting at its ends when grout is back-filled into the groove and compacted.
Another and more specific object of the invention is to provide for such support through means of end caps which have widely spaced feet which may be set over protruding aggregate in the groove.
Still another object of the invention is to provide end caps which accommodate for relative expansion and contraction of the concrete and dowel and are provided with wings which engage opposite slides of the groove to center the dowel within the groove and hold it into place.
Still another general object of the invention is to provide a one piece cap and chair combination which serves to both support the dowel in spaced relationship to the bottom of the groove and to provide for relative expansion and contraction of the dowel and concrete structure.